Gold nanoparticles produced using NaBH4 in absence and in the presence of one-tail or two-tail cationic surfactants: Characteristics and optical responses induced by aminoglycosides

Abstract

Gold nanoparticles (AuNPs), produced using sodium borohydride in water (AuNPs-H), also in the presence of the surfactants cetyltrimethylammonium bromide (AuNPs-CTAB) and didecyldimethylammonium bromide (AuNPs-D10AB), were characterized and investigated in terms of their optical localized surface plasmon resonance (LSPR) response. The automation of the syntheses improved reproducibility of AuNPs. CTAB was chosen as a model one-tail surfactant capping agent for AuNPs and D10AB (two-tail surfactant) was employed for the first time, as a capping agent for AuNPs. Thus, it was possible to carry out a comparative study for the production of AuNPs, varying the surfactant concentration levels from 1.0 × 10−2 to 1 × 10-4 mol L-1. The LSPR profiles were monitored in function of the time, taking into account storage conditions (at 4 °C and at 27 °C). A more unstable behavior was observed for the AuNPs produced in the presence of D10AB at 1.0 × 10-4 mol L-1, which suggested the disassembling of AuNPs over time. The catalytic activity of the AuNPs was evaluated in the presence of 4-nitrophenol, and the most effective kinetics were observed for systems containing the one-tail surfactant CTAB, at 1.0 × 10−2 mol L-1 (8 min), and for AuNPs-H, which has no organic coating, (6 min). Finally, the evaluation of the optical response from AuNPs was conducted with four aminoglycosides (AMG), indicating that these surfactants prevent interaction between AMG and the surface of the nanoparticles since at higher concentrations of CTAB or D10AB there is no significant variation in the LSPR spectral band in presence of AMG. In contrast, strong interaction, observed as variation of LSPR band, was found for the AuNPs-H-AMG systems.